While integrated circuit devices continue to increase in complexity, keeping costs low and form factors small is still a focus for many applications. A key factor in determining the cost and space taken up by a particular integrated circuit device can be the package in which the integrated circuit device is provided.
For integrated circuit devices such as microprocessor chipsets, for example, that are particularly cost- and space-sensitive, a relatively small plastic package having a dense input/output terminal pattern may be used. Ball grid array (BGA) packages, for example, are increasingly popular because they are capable of providing a dense terminal array in a relatively small area at a relatively low cost.
"Terminals" as the term is used herein, refers to external, electrically conductive features provided on a package for transferring signals to and from the integrated circuit die within the package. Types of terminals include pins, solder balls, polymer balls coated with a conductive material, solder columns, land pads, etc. The type of terminal depends on the type of package being used.
To transfer signals to and from an integrated circuit die within a package, bondwires may be used to electrically connect bondpads on the integrated circuit die to bondfingers or bondposts on a package substrate. Individual traces and vias on the package substrate electrically couple the bondfingers to the respective terminals that provide the input/output connections for the package.
The routing of electrical connections from bondpads on the integrated circuit die to the package terminals presents several challenges for integrated circuit package designers. In particular, there may be more bondpads on the integrated circuit die (or bondwires from the integrated circuit die to the package substrate) than there are available terminals on the package. This circumstance may arise, for example, where multiple power and/or ground connections to the integrated circuit die are provided. Multiple power and/or ground connections are desirable in many cases to improve the quality and strength of the signals transmitted to and from an integrated circuit die.
One approach to addressing this issue is illustrated in FIG. 1. FIG. 1 is a top view of a portion of a package substrate 10 having an integrated circuit die 11 mounted thereon. The integrated circuit die 11 includes a double bondpad 12 and two bondwires 13 extending from the bondpad 12 to a double bondfinger 14. The double bondfinger 14 is electrically connected to a single conductive trace 15 extending to a single via 16. The via 16 is electrically connected by a conductive trace on another layer or surface of the substrate 10 to a single power terminal 17 (shown in phantom). The power terminal 17 is coupled to an underside of the package substrate 10. In this manner, the package substrate 10 of FIG. 1 provides for multiple power connections to a single power terminal 17 such that the number of bondpads on the die 11 may be greater than the number of available terminals.
A disadvantage of this approach, however, is that while a ground connection may be provided on either side of the double power connection, a ground bondwire or other ground connection cannot be provided between the two power bondwires 13. Lack of a ground connection between the two power bondwires 13 of FIG. 1 can cause the inductance of the combined power connection to be undesirably high. High inductance can adversely affect device performance.
Further, different types of bondwires and/or integrated circuit device packages including substrates that are different than the substrate 10 of FIG. 1 that have dense terminal layouts may present similar issues.